The engines under discussion may be of the spark ignition type or compression ignition type (Diesel engine). The engines may be turbocharged or charged with air at atmospheric pressure.
Hereinafter, “intake gas” will be understood as fresh air. Moreover, the term “exhaust gas” will be used specifically to denote the gases resulting from a combustion process between a fuel and the air supplied to the engine, recovered at the engine outlet, according to a method generally known by the English acronym EGR (Exhaust Gas Recirculation). Usually, an engine operates by using all of its cylinders according to a known four-stroke cycle: admission—compression—combustion/expansion—exhaust. This cycle is characterized by its efficiency which is recognized as being optimal when the losses due to the transfer of the gases, also called losses due to surging, during the intake and exhaust phases, are minimal.
In order to limit these losses, it has been proposed to deactivate one or more cylinders during operation at low load or more generally when the power required may be provided only by a portion of the cylinders of the engine.
The deactivation is generally carried out by acting directly on the opening of the valves of the relevant cylinders by making them either completely inactive or controlling the valves differently from one another.
However, as no air is supplied to the deactivated cylinder this causes drawbacks. In particular, the temperature in the deactivated cylinder reduces significantly which lowers the overall temperature of the exhaust gases, in particular when restarting the cylinder. Even without the passage of fresh air, this reduction in temperature is harmful to the catalytic converter in the system for treating the exhaust gases.
One solution consists in supplying the deactivated cylinder(s) with exhaust gases recovered at the engine outlet. In particular, as said gases are hot and are able to be returned to high pressure, this makes it possible to maintain the temperature and the pressure in the deactivated cylinder.
The implementation of this device generally requires a means of controlling the flow in at least one of the pipes of the intake manifold making it possible to block the passage of the recirculated exhaust gases or to block the passage of the intake gases, and also a device permitting the communication between an exhaust gas manifold and the volume between the first means and an intake valve for the intake gases.
A hermetic sealing means at the inlet of the recirculated exhaust gases is essential in this case in order to guarantee the seal between the exhaust gas manifold and the intake manifold when the deactivation of a cylinder is inactive, i.e. the cylinder has to be supplied solely with intake gas.
However, the control system for these two means for controlling the flow and the hermetic sealing of the inlet of recirculated exhaust gases, may prove complex, heavy, bulky and expensive. More specifically, two control systems, in particular two mechanical systems which may be independent of one another, are required to control the means for controlling the flow and the means for hermetic sealing of the inlet of recirculated exhaust gases.